(function() {
  document.addEventListener(
    "DOMContentLoaded",
    function() {
      var html = document.documentElement;
      var windowWidth = html.clientWidth;
      html.style.fontSize = windowWidth / 7.5 + "px";
      //等价于html.style.fontSize = windowWidth / 750 * 100 + 'px';
    },
    false
  );
})();
